Apparatus for and method of burning fuel to generate steam



June 3, 1941. M. K. DREWRY APPARATUS FOR AND METHOD OF BURNING FUEL TOGENERATE STEAM Filed Aug. 2, 1937 7 Sheets-Sheet l Monirose K. Drewz'yINVENTOR Wfl f M ATTORNEY.

June 3, 1941. M. K. DREWRY APPARATUS FOR AND METHOD OF BURNING FUEL TOGENERATE STEAM Filed Aug. 2, 4937. 7 Sheets-Sheet 2 MozziroseKDrewqz IINVENTOR.

ATTORNEY.

June 3, 1941. DREWRY I 2,244,144

APPARATUS FOR AND METHOD OF BURNING FUEL T0 GENERATE STEAM Filed Aug. 2,1937 7 Sheets-Sheet 5 Nomz-ose KDz'ewzy INVENTOR.

ATTORNEY.

APPARATUSFOR AND METHOD OF BURNING FUEL TO GENERATE STEAM Filed Aug. 2,193'? 7 Sheets-Sheet 5 Moniwsekiflrewry INVENTOR.

W MW

ATTORNEY.

June 3, 1941. M. K. DREWRY 2,244,144- APPARATUS FOR AND METHOD OFBURNING FUEL T0 GENERATE STEAM Filed Aug. 2, 1 7 Sheets-Sheet 700000000000000V 000000OOOOOOW mm T000 008% ll ll 0 O 0 0 0 0 0 0 O 0 000 000W u: w W K e 5 m n a M 6 6 ATTORNEY.

Patented June 3, 1941 APPARATUS FOR AND METHOD OF BURNING FUEL TGENERATE STEAM Montrose K. Drewry, Milwaukee, Wis., Application August2, 1937, Serial No. 156,866

28 Claims.

My invention relates generally to the art of burning fuel to generatesteam, andmore particularly to improved apparatus for and methods ofgenerating superheated steam in large quantities at high temperatures.In steam generating and utilizing systems, the efficiency of operationmay generally be improved by increasing the size and capacity of thevarious units of apparatus and by increasing the pressure andtemperature of the steam flowing in the system to the highest valuesthat the apparatus is capable of withstanding safely. However, theimproved results attained by these measures are gained only at theexpense of increased difiiculties in successfully operating andmaintaining the apparatus.

In operating a steam generating unit at the higher steam temperatures,the amount of heat used in superheating the steam becomes a largeproportion of the total heat required to generate the steam. Under theseconditions, self-regulation of the steam temperature becomes inadequate,particularly since the amount of heat required to superheat the steamvaries with changes in output of the boiler and with other changes inconditions, with the result that undesirable and uncontrollable steamtemperature variations occur.

In steam generating units of large capacity, the furnace combustionspace volume is very large in proportion to the surface area of theenclosing walls when compared with the relations existing in smallfurnaces. Consequently, proportionately less heat is absorbed by heatabsorbing elements mounted on the'walls of a large furnace and thereforethe temperature within a large combustion space is ordinarily muchhigher than the temperature in a furnace of small capacity operatingunder otherwise similar conditions. High temperatures in the furnacecause melting or fusing of the ashes within the combustion space, withthe result that the ashes coming in contact with heat absorbing surfacesadhere to and collect upon them to the detriment of efficiency and ofuniform conditions of operation. Since the ashes in cooling change frommolten clinging state to dry'state at different points within thefurnace under different operating conditions, deposits of tenaciousashes are formed upon the various heat absorbingsurfaces inuncontrollable and unpredictable patterns.

In a steam generating unit producing highly superheated steam thesedeposits of molten ashes constitute a major problem, since they may re-'sult in materially changing the heat absorbing characteristics, both ofthe associated boiler and of the superheating elements, in such manneras to alter the normal self-regulating character of the unit with theresult that the temperature of the steam may vary considerably underdifferent conditions.

Further, the structural elements of steam generating units operating athigh temperatures are necessarily subjected to high stresses, and anyappreciable variation in the steam temperature may cause difierentialexpansions that result in imposing additional stresses of dangerousmagnitude on the structure, these stresses being of particularly greatimportance since steel and other structural materials are considerablyweakened by high temperatures.

A general object of my invention is to provide an improved steamgenerating unit of large capacity that is capable of continuous, highlyefficient operation.

Another object of the invention is to provide an improved furnace oflarge capacity that is of small size in proportion to the amount of heatgenerated and absorbed in it.

Another object is to provide a furnace arranged to operate withoutexcessive deposits of ash occurring on associated heat absorbingsurfaces and without clinkering of ash in the furnace bottom.

Another object is to provide a steam generating unit having improvedmeans for regulating the temperature of the steam being generated.

Another object is to provide a steam generatingunit capable of beingregulated to control the temperature of the generated steam, and

- that normally operates at a furnace temperature below that at whichash fuses and sticks to heat absorbing surfaces, the arrangement beingsuch that the furnace occupies a minimum amount of erating a steamgenerating unit wherein the temperature of the generated steam may beregulated by adjusting the rate of combustion of fuel adjafuel burningcent to division walls containing superheating tubes.

Another object is to provide an improved method of adjusting a furnaceto change the character of the steam generated by it, that involvesaltering the ratio of water tubes to steam tubes in a dividing wall ofthe furnace.

A still further object is to-provide a convenient and economicalarrangement for cooling ashes and removing them from a furnace.

According to my invention, difilculties previously experienced inoperating large steam generating units, arising from molten ash adheringto heat absorbing surfaces,are obviated by operating thefurnacecombustion chamber at a temperature below that at which the ash fusesand forms slag. This is accomplished by directly absorbing asuificiently large amount of heat as it is radiated from the burningfuel particles, by means of radiant heat absorbing elements disposed inthe zone of greatest heat liberation, to effect the desired temperaturereduction. For this purpose, vertically disposed tubes are arranged toconstitute partial division walls positioned between spaced regions ofintense combustion in the furnace.

Since the entire peripheries of these tubes are exposed to radiant heat,they function to absorb heat in the most efiicient and direct -manner,enabling the combustion space to operate at high capacity, yet atmoderately low temperature. In a powdered fuel burning furnace thedividing walls are disposed 'between spaced fuel burners in manner todivide the otherwise hottest part of the combustion chamber intosections. The tubes in the dividing walls may constitute part of thewater circulating system or part of the steam superheating system, someof the walls being formed by tubes of both kinds arranged :alternatelywith the water tubes serving to support the superheating tubes. Toprovide for regulating the steam temperature, some of the walls may beformed entirely of water tubes, and different proportions of water tubesand steam tubes maybe utilized in the other walls. By adjusting the fuelburners to effect different rates of firing adjacent to these variouswalls, any degree of superheat may be established, the rate beingmaintained under varying load conditions by continued adjustments of theburners as circumstances may require. Various modified arrangements ofthe tubes and of the dividing walls may be employed to meet variousconditions of operation, and adjustments of permanent nature may beeffected readily by altering the ratios of the two types of tubes in oneor more of the walls. Fuels requiring different combustion conditionsmay be burned separately in the different sections of the furnace, andthe furnace may be operated efllciently under low load conditions byburning fuel in only one or two of the sections. Because of the lowoperating temperature in the furnace, the ashes within the combustionchamber fall in dry state and are collected upon a' flat heat absorbingbottom in each section from which they are transferred periodically intoa shielded ash pit provided with conveyors for removing the ashes fromthe furnace.

The foregoing and other objects of the invention, which will become morefully apparent from the following detailed description, may be achievedby the apparatus herein set forth as exemplary of several preferredembodiments of the invention and that is described in connection withillustrative structures depicted in the accompanying drawings, in which:

Figure 1 is a view in vertical cross section of a large steam generatingunit embodying the principles of the present invention, takensubstantially on the plane represented by the lines il in Figs. 2 and 3;

Fig. 2 is a view in vertical longitudinal section of the steamgenerating unit taken substantially on the plane represented by thelines 22 in Figs. 1 and 3 looking into the combustion chamber from thefront;

Fig. 3 is a view in horizontal section of the steam generating unittaken substantially on the plane represented by the lines 3-3 in Figs. 1and 2, looking down into the combustion chamber;

Fig. 4 is a view in vertical cross-section generally similar to Fig. 1,of a steam generating unit embodying a modification of the invention,taken substantially on the plane represented by the lines 4& in Figs. 6and 7;

Fig. 5 is a fragmentary detail view in vertical cross section of amodified ash screen tube arrangement corresponding generally to the ashscreen shown in section in Fig. 2.

Fig. 6 is a view in vertical longitudinal section of the modified steamgenerating unit taken substantially on the plane represented by thelines 66 in Figs. 4 and 7;

Fig. 7 is a view in horizontal section of the modified steam generatingunit taken substantially on the plane represented by the lines l-l inFigs. 4 and 6;

Fig. 8 is a view in vertical cross section, generally similar to Figs. 1and 4, of another steam generating unit constituting a furtherembodiment of the invention, taken substantially on the planerepresented by the line 8-8 in Fig. 9.

Fig. 9 is a view in vertical longitudinal section of the furthermodification, taken substantially on the plane represented by the line99 in Fig. 8;

Fig. 10 is a somewhat diagrammatic view in horizontal section, generallysimilar to Figs. 3 and 7, showing another arrangement of dividing wallsconstituting a further modification of my invention;

Fig. 11 is a view similar to Fig. 10 but showing a different arrangementof tubes in the dividing walls;

Fig. 12 is a somewhat diagrammatic view in vertical section, generallysimilar toFigs. 1 and 4 showing an arrangement of dividing wall tubesconstituting. a still further modification of my invention.

Fig. 13 is a somewhat diagrammatic plan view of part of a division wallshowing the manner in which the superheating tubes are supported inwater tubes; and

Fig. 14 is a fragmentary view in elevation of the interlocked divisionwall tubes shown in Fig. 13.

Referring more particularly to the drawings,

and especially to Figs. 1, 2 and 3 thereof, the steam generating unitthere illustrated as constituting structure exemplifying a preferredembodiment of my invention, includes a vertically fired pulverized fuelburning furnace associated with and furnishing heat to a boiler of thethreedrum bent-tube type.

' The furnace element of the unit comprises an enclosed unitarycombustion chamber 20 into which mixtures of pulverized fuel and air areprojected at spaced positions for burning in a plurality of distinctzones of intense combustion,

and at the front of the furnace from which the coal descends through afeeder or control valve and is delivered in measured quantities into apipe 24 leading to the associated burner. Primary air for projecting thecoal from the burner intothe combustion chamber and for providing partof the oxygen to support combustion, enters each of the pipes 24 from aprimary air duct 25, a control valve or damper 26 being provided forregulating the flow of air to each burner individually.

By adjusting the fuel feeder 23 and the primary air valve 26 associatedwith each burner,

the rate of fuel consumption and the amount of heat liberated in thecombustion zones supplied by the various burners may be individuallyreg-J ulated.

disposed vertically in side by side relation at the front of thefurnace, as shown in Figs. .1 and 3. A duct 28 extends lengthwise of thefumace above the'air boxes 21 and supplies air to each. of them throughan individual control valve .or

damper 29 that is adjustable to regulate the supply of secondary air toeach pair of burners. From the air boxes 21, the secondary air flowshorizontally through. vertically spaced openings 6 I 30 ina forward wall3| of the combustion chame ber in-inanner to mix with the fuel andtheprimary air descending from the burners 2|. The flames from each of theburners 2| extenddownward into the combustion chamber 20 and constitutespaced zones of maximum combustion in the regions directly below thevburners :where the fuel mixes with the inflowing secondary air and thegreater part of the combustion and heat liberating reaction occurs. I

The secondary air flowing horizontally through the openings 30 causesthe flames to curve back into the rear part of the combustion chamberand to turn upward therein as indicated by the arrows in Fig. 1. Theflames from the several burners intermingle and equalize in temperatureas they curve upward in the back part of the combustion chamber, theprocess of combustion being slowly completed in this region.

The hot gases resulting from the combustion process flow upward from thecombustion chamber 20 under the influence of the furnace draft into theboiler, passing along and through a bank of boiler tubes through whichwater circulates upward from a mud drum 36at the bottom of the boiler toa steam drum 31 at the top thereof, a baflle 38 being provided forcausing the 'hot gases to flow in the direction generally longitudinallyto a. second steam drum 4| disposed adiacent to and parallel with thefirst Steam drum 31.

The hot gases enter the tube bank 40 in the region immediately above themud drum 36, and flow upward parallel with the tubes 40 between thebailie 39 and a bailie 42 extending, upward from the mud drum.Immediately below the flow downward parallel with these tubes betweenthe baflle 42 and a battle 44, the baflle 44 constituting the rear wallof the boiler setting and part of a duct 45 through which the gases passfrom the boiler to be discharged up the stack.

Ashes remaining after the combustion of the coal in the combustionchamber 26, descend into an ash pit 49 beneath the furnace, from whichthey may be removed periodically by way of doors 50 provided in the backwall of the ash pit for that purpose. In order to cool the ashes as theydescend into the ash pit, to therebyprevent the formation of clinkers,and to utilize heat in the ashes which would otherwise be wasted, aplurality of heat absorbing tubes5| are disposed, substantiallyhorizontally across the bottom of the combustion chamber in spacedrelation to constitute a water screen. As the ashes fall onto andbetween the spaced tubes 5| of the water screen they give up sufficientheat to the tubes to prevent the ash particles from sticking tov thetubes or coalescing in the bottom of the ash pit. Further functions ofthe tubes 5| are to shield the ash pit from the heat radiated from theflames in the combustion chamber 2|] and to asorb'heat passing upwardfrom the ashes in the 'ash pit. v

,The' tubes 5| of the water screen-are connected in the watercirculating system of the boiler, water for. flowing'through them beingbrought down from the mud drum 36 through downcoming pipes 52, whichpass outside of the furnace, to an inlet header 53 disposedlongitudinally of the furnace at the rear thereof and below the bottomof the combustion space, asshown in Fig. l. 'Each of the screen tubes 5|is connected at one end to the header 53, the tubes extending forwardlyfrom the header with a slightly upward inclination across the bottom ofthe combustion chamber to a header 54 disposed longitudinally of thefurnace at the front thereof immediately below the air boxes 21.

From the header 54, a bank of tubes 55 extends substantiallyhorizontally back into the combustion chamber 20 in manner to form ascreen at v the top of the chamber in the region of the downof the tubes'35 until they reach the portions.

thereof immediately below the steam drum 31.

In the region of the steam drum 31 the hot 46 which extend upward fromthe mud drum 36 I front of the combustion chamber is exposed to. heatradiated directly from burning fuel parti-' cles in the zones of maximumcombustion below wardly projecting burners 2|. These tubes then turnupwardly along the inside of the upper front wall 58 to' the top of thefurnace where they connect with and discharge into the forward steamdrum31.

The water wall formed by the tubes 55 at the the burners 2|. Radiantheat emitted from the burning fuel is likewise absorbed by the waterscreen'tubes at the bottom of the combustion chamber and by the tubes 51at the top thereof. Furthermore, banks of radiant superheater tubes 60are disposed at each end of the combustion chamber to absorb additionalradiant heat, these banks also serving to protect the end walls H of thefurnace structure. Likewise a bank of radiant resuperheating tubes 62 ismounted on" and protects the back wall 53 of the furnace. The mostefl'icient method of absorbing heat liberated by burning fuel is toabsorb the heat as it is transmitted by direct radiation fromincancombustion chamber 20 is covered with heat absorbing tubes arrangedin various banks as previously explained. To operate a furnaceconstructed in this manner successfully, it is necessary to maintain thefurnace temperature sufliciently low to avoid overheating the heatabsorbing tubes.

Because of the fact that the volume of a furnace combustion spacechanges with the cube of its linear dimensions while the wall areachanges with the square of its linear dimensions, as furnace sizesbecome larger the proportion of wall surface area to combustion spacevolume becomes materially less. Consequently, in very large furnaces,the radiant heat absorbing elements on the-combustion chamber wallscannot absorb suflicient heat, unless the furnace is operated at verylow rating, to aintain the temperature in thecombustion space below thatat which the ash coalesces. Under conditions of excessive temperature inthe combustion chame her the fusing ashes adhere tenaciously to andinsulate the heat absorbing surfaces, thereby further reducing theamount of heat absorbed by them with the result that the furnace becomesstill hotter. For these reasons, furnace volumes have in the past beendetermined in accordance with the permissible furnace temperatures,rather than by other factors such as considerations relating tocombustion reactions or the like.

In accordance with my invention, the difficulties heretofore encounteredin furnaces of large size resulting from excessive temperature in thecombustion chamber, are overcome by providing additional radiant heatabsorbing surfaces at positions in the combustion chamber favorable toabsorbing most effectively the heat radiated from the burning fuel.. Tothis end, the additional radiant heat absorbing elements are positionedbetween the spaced zones of maximum heat liberation occurring beneaththe various burners,

, in manner to present both sides thereof toward [the flames from theburners to directly absorb the heat radiated from the burning fuelparticles.

As illustrated in the drawings, the additional heat absorbing elementsare arranged to form vertically disposed division walls between thegroups or pairs of burners 2!, the walls being exposed at both sides oheat radiated from the flames. As may best be seen in Figs. 2 and 3, theparticular furnace illustrated is provided with five division wallsdesignated respectively, A, B, C, D and E, which divide the forward partof the combustion chamber into six open-sided compartments or sections,each section being served by a pair of burners 2| and by one of thesecond ary air boxes 21. As shown in Figs. 1 and 3, the division wallsare disposed primarily in the region' of maximum combustion at the frontof the combustion chamber in order that they may function at maximumefficiency in absorbing ra diant heat, the back part of the combustionchamber in which heat transfer rates are low being left open to permitintermingling of the combustion gases from the various sections in orderto equalize the flow of gases into the boiler.

By this arrangement of the additional heat absorbing tubes, highlyefficient absorption of heat radiated directly fromthe burning fuelparticles is accomplished, and furthermore the tubes function at higherrates of heat absorption than do tubes exposed at only one side toradiant heat. Because of the highly eflicient performance of the heatabsorbing elements in the division walls, a greater amount of heat isabsorbed in proportion to the total heat absorbing surface of thefurnace and boiler than was formerly possible. This increasedeflectiveness coupled with the fact that the total radiant heatabsorbing surface area in the furnace is materially increased by theaddition of the division Walls, results in much higher heat absorbingcapacity in a furnace of a given size, or permits a. furnace of givencapacity to be made much smaller than has heretofore been practicable.

Although the size of the furnace may be materially reduced as a resultof the additional radiant heat absorbing surface provided by thedivision walls, the temperature in the combustion chamber 20 is,nevertheless, actually reduced because of the increased rate of heatabsorption to a point below that at which'the ashes resulting from thecombustion of the coal fuse and coalesce upon the heat absorbingsurfaces in the furnace or upon the tubes in the boiler proper. Byreason of the low temperature thus maintained in the combustion space,the ashes remain in dry state and fall as. separate particles into theash pit 49 without adhering to any part of the furnace. Since thefurnace heat absorbing surfaces are kept ,free from clinging ashes inthis manner, uniformly high heat absorbing efficiency is attained anduniform response to adjustments for effecting regulation of the steamtemperature is assured.

As a further result, the eificiency of the combustion process isactually increased by the reduction in thefurnace temperature, for thereason that the gases in the combustion chamber, 20 are not as rarifiedand do not occupy as much space as do the gases in a highly heatedfurnace and more time is thus afforded for the combustion reaction.

By disposing the division walls in the front in the rear or secondarycombustion zone where very little radiant heat from burning coalparticles is available, the average heat absorption rate would bematerially reduced. Furthermore, the beneficial effects upon combustionemciency occur in the zone of greatest combustion and highesttemperature where it is desirable to reduce the temperature. on theother hand it is desirable to permit the temperature in the back of thefurnace to increase in order to improve combustion in the secondarycombustion zone. By this arrangement of the tubes, both of theseconditions are met, and the temperature throughout the furnace is thusmaintained more nearly uniform and at the point most conducive tocomplete and highly efficient combustion.

The heat absorbing elements forming the division walls may be watertubes or they may be superheater tubes, the water tubes constitutingpart of the water circulating system of the boiler. As shown in Fig. 1,water for circulating upward through water tubes 65 in each divisionwall, flows from the header 53 at the back of the furnace through aplurality of bent tubes 61 disposed below the screen tubes into a shortheader 68 beneath each division wall, the headers 68 being connected tothe lower ends of the vertical water tubes 66. At their upper ends thetubes 66 are connected to headers 69 disposed parallel with the headers68 and above the-hori+ zontal portions of the tubes 51. Each of theheaders 69 is joined at its inner end to a transverse header 10, theheaders being disposed in alignment lengthwise of the furnace. thetransverse headers 10 a plurality of tubes extend upward inside theupper front wall 58 and parallel with the tubes 51, to the upper part ofthe boiler where they connect with the front steam drum 31.

Steam generated in the boiler tubes or in the furnace tubes passesupward into either the steam drum 31 or the steam drum 4|, the two drumsbeing connected by tubes 13 to permit flow of steam from the drum 3'! tothe drum 4|. From the steam drum 4|, a plurality of tubes 74 lead to asuperheater inlet header 15 from which the steam flows into the tubes ofa convection superheater 16 that is disposed between the baflies 38 and39 and in the path of the hot furnace gases. The tubes of thesuperheater 16 connect with and discharge into a header H from each endof which the steam is withdrawn in superheated condition through pipes18.

An important feature of my invention is to From provide means forregulating the temperature of the steam in. such manner that steam ofuniform temperature may be supplied to steam consuming apparatusregardless of changing loads or other varying conditions. To this end,additional superheating elements of the radiant heat absorbing type areplaced in and constitute part of some of the division walls, the"arrangement being such that the amount ofsuperheating effected by themmay be regulated by adjusting I the amount of fuel consumed in theburners the ends of the furnace and turn inward near a the burnerstoconnect with inlet headers 80 disposed above the division walls A and E,respectively. From the headers 8|! superheating tubes 8| pass downwardwithin the division walls A and E between spaced water tubes 66, as bestshown in Fig. 3, and then' return upward to connect with dischargeheaders 82 disposed parallel with and just below the inlet headers 80.From the headers 82 the superheated steam flows through pipes 83 out tothe ends of the furnace and downward to headers 84 to which one end ofeach tube of the radiant superheater bank in each end of the furnace isconnected. The other ends of the tubes are connected to dischargeheaders 85 disposed just below and parallil with the headers 84.

After passing through the end wall superheating elements to the headers85, the steam at the regulated temperature is conducted away throughpipes 85 to steam consuming apparatus such as a steam turbine. From theturbine some of the steam may be returned for resuperheating, the returnpiping being connected to an inlet header extending along the back wall63 of the furnace to which one end of each of the tubes 62 of the rearwall resuperheating tube bank is connected. The other end of each tube62 is connected to a header 9| disposed parallel with and below theheader 9!! and from which the resuperheated steam is returned to theturbine.

As the superheating tubes 8| in the division walls A and E are. exposedto radiant heat at both sides and operate at relatively hightemperatures, it is desirable that eachsuperheating tube be disposedadjacent to a water tube 66 which serves to support it in manner toprevent it from warping. As shown in detail in Figs. 13 and ,14, thewater tubes 66 in the division walls A and E are provided on each sidethereof, and in the plane of the wall, with vertically spaced projecting1ugs93 that engage similar lugs 94 on the sides of the adjacentsuperheater tubes 8|, the lugs being disposed alternately and interlacedas indicated in Fig. 14, to prevent movement of the superheatin-g tubes8| in either direction out of the. plane of the division wall.

When changes in operating conditions make it desirable to regulate thetemperature of the steam supplied to the steam consuming apparatus, theburners 2| adjacent to the end division walls A and E may be adjusted toregulate the amount of heat supplied to the radiant superheatingelements in these walls. For example,

if the steam temperature becomes too low, the

amount of fuel being consumed by the burners disposed between each ofthe'end' division walls A and E and the tube banks 60 on the respectlveend walls 6|, may be increased to increase the amount of heat absorbedby the superheating tube banks 60 and the superheating tubes 8| in theend division walls, thereby increasing the superheating effect andraising the steam temperature. In case a further increase in the steamtemperature is required, the burners dis- Posed between the divisionwalls A and B and those between .the division walls D and E may also beadjusted to increase the amount of heat supplied to the tubes 8|.

If it is desired to maintain the total fuel consumption of the furnacesubstantially constant under these conditions, the increased amount offuel being consumed in the end sections may .be compensated for bycorrespondingly reducing the amount of fuel being consumed by theburners in the two central sections between the division walls B and D.Conversely, if the steam temperature becomes too high, the amount offuel being consumed in the end sections may be reduced to effect areduction in the steam temperature. Likewise, the amount of fuel beingconsumed in the central sections may then be increased to balance thetotal fuel consumption.

In modern steam generating plants utilizing high temperature steam,changes in load on the steam consuming apparatus may result in greatlychanging the amount of heat required to generate the steam and theamount of heat required to superheat it to the desired temperature.These conditions can be compensated for, in a steam generating unitconstructed in accordance with my invention, by adjusting the burners toregulate the steam temperature as :previ-' ously explained.

Further adjustments of steam temperatures may be effected by changingthe positions of the flames projected from the burners, this beingaccomplished by regulating the flow of primary and secondary combustionair into the furnace. Thus if it is desired to decrease the amount ofheat being absorbed by the division walls and to increase the amount ofheat being absorbed by the resuperheater tubes 62 on the back wall 63 ofthe furnace to thereby increase the temperature of the resuperheatedsteam, the amount of secondary air being admitted horizontally throughthe openings 30 in the front wall 3| may be increased to cause theflames emanating from the sections to be displaced toward the rear ofthe combustion chamber to increase-their heating effect upon the tubes52. total amount of air supplied for supporting combustion and to delaythe combustion of the fuel, the amount of primary air being suppliedthrough the burners may be correspondingly reduced.

- This method of adjusting the temperature of the resuperheated steammay be used in conjunction with the previously explained method ofadjusting the initial steam temperature in order to attain completecontrol of the various steam temperatures. If the bank of tubes 62 onthe rear wall of the furnace were connected to constitute part of thesuperheating surface, displacement of the flames toward the rear wallwould result in reducing the amount of heat absorbed by the water tubes55 on the front wall and the water tubes 66 in the division walls, and

in increasing the amount of heat absorbed by the superheating tubes 62,thereby increasing the temperature of the steam.

Because of the fact that ashes do not adhere to, the heat absorbingsurfaces in a furnace operated in accordance with this invention, theheat absorbing characteristics of the various water heating and steamsuperheating elements remain substantially uniform, and consequently theeffect of adjusting the burners to regulate the steam temperature issubstantially the same at all times.

If it is found desirable to effect an adjustment of permanent nature inthe normal temperature of the steam being generated, the desired resultsmay be accomplished readily by altering the ratio or proportion of watertubes and steam superheating tubes in one or both of the end divisionwalls A and E. If the steam temperature is to be lowered, it is merelynecessary to remove one or more of the superheater tubes 8i from thedivision wall and to substitute water tubes 66 for them. Conversely, toincrease the steam temperature, water tubes may be removed and Tobalance the superheater tubes substituted. This adjustment may be madeconveniently, with the furnace shut down, since the tubes in thedivision walls are interchangeable and are readily accessible, thevarious headersbeing so positioned as to permit substitution ofsuperheater tubes for water tubes or vice versa without dimculty.

In a steam generating unit constructed in accordance with my invention,the danger of overheating the radiant superheater tubes beforesufficient steam is generated to pass through them is obviated by firststarting the fuel burners 2| positioned between the division walls B andC and between the division walls 0 and D. Since these division wallscontain only water circulating tubes they are capable of immediatelyabsorbing the heat from the burners without injury. After sufficientsteam has been generated by operating the burners in the centralsections of the furnace to provide a flow of steam through thesuperheater tubes, the burners in the end sections may be started andthe final steam temperature regulated by adjusting the-various .burnersas previously described. After one or more of the burners have beenlighted it is not necessary to light the subsequently started burnersindependently since the flames from one burner will pass between thetubes of the division walls and ignite the coal introduced through theadjacent burners.

An additional advantage of the sectionalized furnace resides in the factthat different grades of fuel requiring different combustion conditionsmay be burned in separate sections of the furnace simultaneously bysuitably adjusting the fuel feeders 23, the primary air valves 28 andthe secondary air dampers 29 individually in each section to effect theconditions most favorable to the combustion of the particular fuel beingfed to that section.

Another important advantage of the sectional arrangement in the furnaceis that when operating at low loads some of the burners may be turnedoil entirely and the load carried by the burners in only one or two ofthe sections. Since each section is in effect a small independentfurnace, any one or more of the sections may be operated efliciently asa generating unit of reduced capacity. As the effective heat absorbingarea is correspondingly reduced because the radiant heat reaches onlythe adjacent division walls, the necessary furnacev temperature ismaintained, the hot gases of combustion spreading in the back of thecombustion chamber and flowing uniformly into the boiler tube banks. Byoperating individual sections of the furnace in this manner, it ispossible to avoid the necessity of shutting down a large furnace andstarting a smaller one in order to maintain eflicient operation at lowloads.

The particular arrangement of apparatus set forth in the foregoingdescription is but one of many possible combinations which may beutilized in practicing my invention under'various conditions of steamrequirements and of load variations. Obviously, the invention may beembodied in steam generating units of various other types with equallyadvantageous results. For example, the steam generating unit shown inFigs. 4 to 7 inclusive, as another embodiment of my invention, differssomewhat in arrangement from the apparatus shown in Figs. 1 to 3 butincorporates the features constituting the principal aspects of theinvention. In this ar rangement, the boiler is of the two-drum type andis disposed at the back of the furnace.

As shown, the furnace comprises an enclosed combustion chamber I intowhich fuel is projected by a plurality of spaced, vertically disposedburners IN, the burners being individually controlled in avmannersimilar to that described in connection with the burners 2i shown inFigs l and 2. Secondary air is admitted from air boxes I02 at the frontof the furnace under the control of individual dampers I03, the

air moving horizontally through openings in the front wall of. thefurnace into the chamber I00 and carrying the flames from the burnersIM- steamdrum I06 near the top thereof, the gases,

having been guided upward by a baiiie I01. Near the steam drum I thegases flow over the top of the baflie I01.'and downward between it and abaiiie I08 to a point near the mud drum I05 where they enter anotherbank of boiler tubes I09 also extending upward from the mud drum I05 tothe steamdrum I05. The gases are guided upward parallel with the tubesI09 between the baiile I08 and an outer baflie "I I0 constituting therear wall of the furnace, and they are then discharged at the top of theboiler into a duct II I leading tothe stack.

As best shown in Figs. 6 and 7, the combustion chamber IIIII'is dividedinto five compartments or sections by vertically disposed division wallsof heat absorbing tubes designated respectively H, I, J and K, the wallsextending back toward the boiler tubes I04, suflicient space beingprovided beyond the ends of the walls to permit equalization of thegases flowing from the different furnace sections into the boiler.

-Water for circulating upward through the water tubes of the divisionwalls flows from the mud drum I05 through a plurality of tubes II5 Iinto transverse headers H6, Figs. 4 and 'I,- each of which is joined atright angles to a header II1 disposed beneath each of the divisionwalls.

From each of the headers II1, water tubes '8 sorbing elements extendupward to a header 9 disposed at the top of the wall and parallel withthe corresponding lower header II1. Each of the upper headers II 9 isconnected to a transconstituting part of the division wall heat abverseheader I20 from which the water flows through a plurality of tubes I2Iinto the steam drum I06.

Steam generated 'in the water tubes of the boiler or of the divisionwalls passes upward into the steam drum I05 from which it passes throughtubes I24 into a header I25 andthence into the tubes of a convectiontype superheater I25 that is disposed between the baffle I01 and thebaiile I08 in the path of the hot furnace gases flowing through theboiler. From the su- -perheater I25 the steam flows into transverseheaders I21 each of which is' connected to a header I25 extending atright angles thereto respectively. From thehead-ers I28 radiantsuperheating tubes I30 extend downward in the division walls 1-! and Kbetween the water tubes and overlying the and division walls H and K vH0 thereof, and return upward thereinto connect with headers I3Idisposed above and parallel with the headers I28, the superheating tubesI30 constituting additional radiant heat absorbing elementsin thedivision walls. From the headers I3'I the steam flows through aplurality of tubes I32 to headers I33 disposed respectively at the endsof the furnace parallel with. and adjacent to end-walls I34 thereof. Theheaders I33 are each connected to a pluralityof radiant superheatingtubes I35 which extend downward along the inner side of each end wallI34 and return upward to connect to headers I35 disposed below andparallel 'with the headers I33.- The radiant superheating tubes- I35constitute banks of heat absorbing elements that function to protect theendwalls I34 from the intense heat of the combustion chamber. From theheaders I35 steam may .be conducted to a steam turbine orother steamconsuming apparatus by pipes connected to flanges I31 at the ends of theheaders I35. v

By regulatingthe various fuel burners ,IOI in a manner to increase ontodecrease the amount of fuel being consumed adjacent to the radiantsuperheater tube banks I35 on the end walls I30, and adjacent to theradiant superheater tubes I 30 in the divisionalwalls H and K, thetemperature of the steam being delivered from the discharge header I 36may be raised 'or lowered, as desired.

Since radiant superheating tubes will fail if overheated, it isnecessary in order to successfully utilize them, that they be operatedat relatively low heat transfer rates, hence high temperatures in thecombustion chamber must be avoided. In a furnace constructed inaccordance with my invention, the large total area of heat absorbingsurface presented in thercombustion chamber, together with the fact thatthe heat absorbing division walls are disposed in the zone of greatestheat liberation, result in suflicient heatbeing absorbed directly fromthe burning fuel particles to reduce the temperature in the combustionspace below thatat which the radiant superhe'ater tubes might becomeoverheated. Because of the high rate of heat absorption and therelatively low temperature in the combustion space, it becomes practicalto utilize radian-t superheating tubes in the heat absorbing divisionwallsand in the banks of tubes at the ends of the combustion chamber,and to employ this arrangement of tubes in a furnace of very largecapacity in which it would otherwise be impractical to use radiant'superhe'ating elements.

to employ an improved method or disposing oi."

the ashes.

In the embodiment of the invention shown in Figs. '4, 6 and 7, the ashesremainingafter combustion of. the coal, descend in the combustionchamber onto a plurality of water cooled flat plates I40 constitutingrespectively the bottoms of the several furnace sections and forming anearly continuous ash receiving surface for the bottom of the combustionchamber. As best shown in'Flgs. 4 and 6, the several plates I40 aresupported upon and cooled by water circulating ,before they becomecovered with ash, thereby insuring complete combustion of the fuel.

Before the ashes accumulate sufficiently 'to 1 form a layer of suchvthickness as to insulate the plates I40 enough to interfere. materiallywith the absorption of heat from additional ashes as they fall from thecombustion chamber, the layer of ashes is removed from the plates bymeans of tools or preferably by soot-blowers I42 or the like. Thesoot-blowers may be operated to direct jets of steam or of air againstthe ashes periodically before they become hot enough to fuse, to blowthem' from the plates into intervening openings I43 through which theyfall into the ash pit I44. The soot-blowers can be arranged to operateautomatically to remove the ashes at predetermined intervals, ifdesired.

As shown in Fig. 6, the openings I43 are formed by spaces between theedges of adjacent plates I40 and they occur at the vertical divisionwalls thereby providing passageways permitting ashes which accumulateonthe walls to fall directly into the ash pit I44. The ash receivingplates I40 serve to shield the ash pit 144 from the heat of thecombustion space, and the plates and supporting water circulating tubesI41 serve to absorb heat radiated upward from the ashes in the ash pit.This results in cooling the ashes to such. extent that little heat islost with them when they are removed and mechanical conveyors may beutilized to remove them from the ash pit without danger of the conveyorsbecoming over heated. For this purpose screw conveyors I45 may beinstalled as shown in Figs. 4 and 6, preferably beneath the openings I43between ad'- jacent bottom plates I40, where the greatest accumulationof ashes occurs. An ash receiving furnace bottom of this type ispracticable only in a furnace in which the temperature is maintainedrelatively low. Ifv the temperature were held still lower, by directlyabsorbinga much larger amount of heat, it would be possible to dispensewith theash cooling, elements altogether and to permit the ashes to falldirectly into the ash pit. In that case a conventional furnace I tubesI4I are connected at the rear of the furnace to the mud drum I05. Fromthe drum I05,

boiler water flows forward through the tubes I4l to a header I46, towhich each of the tubes is connected, the header being disposedlongitudinally of the furnace just below the secondary air boxes I02 atthe front of the furnace. From the header I46 a banker tubes I41 extendsupwardly along'the inner surface of the frontwall I48 of the furnace,serving to shield the wall from the intense heat in the region ofmaximum combustion where the secondary air enters the combustion chamberand mixes with the fuel descending from the burners I I. At the top ofthe combustion chamber, the tubes I41 are curved inwardly and extendhorizontally along the top of the chamber to the rear thereof where theyconnect with the steam drum I05.

may be replaced by two banks of spaced screen tubes II disposed instaggered relationship. The

screen tubes I 5| serve to completely shield the ash pit I44 fromradiant heat and yet they provide spaces through which the ashes maydescend freely into the ash pit. To maintain high heat absorbingefliciency in the screen tubes I5I, sootblowers may be provided todislodge ashes which may accumulate on or between them.

In another embodiment of my invention, shown in Figs. 8 and 9, theboiler portion of the steam generating unit is disposed above thefurnace and the fuel is introduced into the furnace horizontally. Asshown in Fig. ,8, the furnace comprises an enclosed combustion chamber I60 into which the fuel in projected by means of a plurality ofhorizontally disposed burners I 0I arranged in horizontally spacedrelationship in the lower part of a front wall I62 of the furnace.

The burners I61 may be generally similar to the previously describedburners 2| and I M and they are arranged to be individually adjustablein like manner, the secondary air being admitted through an air box I53encircling each burner.

The flames from the burners I6I extend horizontally into the combustionchamber I60 and baflle I06. At the top of the furnace, theboiler tubesI64 bend back inwardly and extend horizontally to a steam drum I61 atthe rear of the furnace, the gases passing horizontally over a battleI58 disposed beneath and extending parallel with the tubes, and thenescaping upward protecting screen shielding the rear wall from theflamesprojected from the burners I6I. At

the top of the combustion chamber I60, the tubes I14 are bent forwardlyfrom the wall I12 and extend across the top of the chamber in twostaggered rows, inclined slightly .upwardly, to the mud drum I65.

As shown in Fig. 9, the combustion chamber I is divided into threecompartments or; sections by means of two vertically disposed divisionwalls designated L and M. The division walls in this instance extendentirely across the combustion chamberfrom front to back and each iscomposed of both water tubes and superheater tubes disposed verticallyand alternately arranged verse headers I15,- joined at right anglesthereto and disposed respectively beneath the division walls. Watertubes I15 in the division walls extend upwardly from the headers I15 toparallel headers I11 at the top of the combustion chamber which areconnected directly to the mud drum I65.

The bottom of each section of the furnace is provided with an ashreceiving plate I00, the plates bei supported upon and cooled byhorizontally dis sed water tubes IlI which extend forward from theheader I13 and turn upwardly along the inner surface of the frontfurnace wall I62 to the mud drum I85. Ashes which accumulate on theplates I80 are blown from them by' soot-blowers I82 through openings I83between the. edges of adjacent plates, into an ash pit I84.

Steam generated in the various water tubes of the furnace and theboiler, passes upward throughthe boiler tubes I64 into the steam drumI61 from which it passes through tubes I88 into a header I 89 below thesteam drum. From the header I89 the steam fiowsinto tubes I90 of aconvection type superheater disposed directly above the combustionchamber I60, beneath the horizontal baflle I68 and back of the verticalbaflie I88. Hot gases from the combustion chamber flow upward betweenthe superheater tubes I90 and pass through an opening I9I provided Fromrangement steam may be returned from the turbine several times forsuccessive reheatings, the various superheating elements beingindividually controlled, in accordance with myinvention, to

provide the desired degree of steam temperature in each stage. Bysuitably rearranging the connecting piping, a boiler constructed inaccordance with my invention may be utilized to heat two differentfluids. For instance, the boiler and part of the superheaters may beused to evaporate mercury and to superheatit, respectively, while othersof the superheating elements are used to superheat and to resuperheatsteam supforwardly over the division walls. From the headers I94 thesteam flows downward through radiant superheater tubes I95 in thedivision walls Land M, the tubes returning to headers I96 disposedbeneath the headers I94 and connected to a discharge header I91 at therear of the furnace.

Adjacent to each end wall 202, a header 203 extends. forwardly from theheader I98 to deliver steam from the convection superheater tubes I90 toradiant superheater tubes 204 extending downwardly along the innersurface of the end walls. 202 and returning to headers 205 disposedbeneath the headers 203 and likewise connected to the discharge headerI91. From the discharge header I91 the steam maybe conducted, throughpipes connected to flanges 200 at the ends thereof, to the steamconsuming apparatus.

The temperatureof the steam supplied to the discharge header I91 may beregulated, in accordance with my invention, by adjusting the ratio ofthe-fuel supplied by the middle burner between the division walls L andM, to that supplied by the end sectionburners between the' divisionwalls and the respective end walls. Since the banks of tubes at the endwalls are made up entirely of superheater tubes, an increase in theamount of fuel burned, adjacent tothem tends to increase the steamtemperature, and converse-' ly a reduction in the amount of fuelconsumed in the end sections tends to reduce the steam temperature. Manyother variations in the arrangement and disposition of the parts ofsteam generating units constructed according to my invention may be madeby persons skilled in this art. For example, the various divisional orseetionalizing walls in the combustion chamber may be adjustedindividually to contain any desired ratio of superheating tubes andwater tubes. Further, the divisional walls may be so positioned in thecombustionchamber as to form fur-, nace compartments or sections havingdifferent volumes to better adapt the furnace for meeting particularconditions of operation. Under other conditions, it may 'be'desirable toconnect the superheating elements in manner to provide several differentstages of superheat. By this arplied from other sources.

Other variations in the structure may be made to improve the efliciencyof heat absorption un--,

der various particular conditions of operation.

As the amount of heat radiating from the gases and burning 'iuelparticles ina furnace depends largely upon the degree of concentrationof the burning fuel particles, maximum heat absorption efliciency maybeattained by absorbing heat the highest concentration of burning fuelparticles, as indicated diagrammatically in Fig. 10. As there shown, afurnace having an enclosed combustion chamber 2| 0 into which aplurality of burners 2 project fuel at spaced positions, is providedwith .heat absorbing division walls disposed respectively between eachtimer and the next adjacent burner, the walls being designated N, O, P,Q, R, S and T, respectively. By separating each burner from the adjacentburners in this manner by heat absorbing division walls, large amountsof heat are absorbed in the regions closely adjacent to the burners,since the burning fuel particles are highly concentrated in that part ofthe combustion chamber. However, as the flames move back into thecombustion chamber, the amount of heat radiated from them decreases asthe concentration of burning fuel particles decreases, and it is notnecessary to provide as much heat absorbing surface as is .requiredcloser to the burners. For this reason,

heat from the burning fuel particles remaining in the flames thatproject beyond the ends of the short walls. Likewise, thewalls O and Sextend about one-half way across the combustion chamas indicated by thedivision walls X, Y and Z shown in Fig. 1d, from close spacings in theregions of high heat absorption adjacent to they burners, to widespacings toward the rear of the furnace.

The numbers and width of the various walls and the spacings of the tubesin each wall may i be so. selected in any particular steam generat- 8unit-as to result in best heat absorbing efliciency, when taking intoaccount the cost of the tubes in the division walls, the kind of fuel tobe burned, and other factors.

As another variation, the division walls may be formed of curved tubesas indicated in Fig. 12, the tubes being-more widely spaced near thebottom of the combustion chamber than near the top thereof. Theapparatus represented diathe header 69, conforming approximately withthe paths of the flames from the burners 2|. By this. arrangement of thetubes H5 and H6, the division walls are made to conform in widthapproximately to the width of the flames as they descend from theburners. Consequently, the tubes are disposed in a manner to absorb themaximum amount of heat radiated from the burning fuel particles in theflames.

From the foregoing descriptions of the several embodiments of thisinvention and the explanation of the mode of operation thereof, it isevident that there has been. provided a new and improved steamgenerating apparatus, utilizing a new method of generating steam, thatis, capable of furnishing steam in large quantities and of predeterminedquality, the arrangement being such that space is conserved yet highlyeflicient operation is effected at moderate furnace temperatures withentlrefreedomfrom fusion of ash and complete control of steamtemperature.

Although specific embodiments of my invention' have been shown anddescribed in detail to illustrate operative'apparatu's functioning inaccordance with the invention, it" is to be understood that variousother modified structures may be devised by those skilled in this art,in order to utilize the principles -herein,set forth, without departingfrom the spirit and scope of the invention as it is defined in thesubjoined claims.

I claim as my invention:

1. A powdered fuel steam generating unit, comprising an enclosureconstituting a combustion chamber, a boiler including water tubesdisposed to behea'ted by hot gases flowing from said combustion chamber,a plurality of fuel burners disposed to project powdered fuel into saidcombustion chamber at spaced positions, water tubes and superheatertubesconnectcd to said boiler ,ash receiving surface at intervalstoprevent. them from accumulatlng'to sufllcient thickness to in- 1terferefwith the coolingaction of said cooling member.

. :ZMA, steam generating apparatus, comprising a furnace constituting acombustion space, a boiler having convection water heating surfacesexposed to hot gases from said combustion space,

division walls having radiant water heating surfaces and division wallshaving radiant steam superheating surfaces disposed within saidcombustion space, fuel burners in said combustion space providing heatfor said convection water heating surfaces and including a burnerdisposed to provide radiant heat to one of said division walls havingradiant water heating surfaces and a burner disposed to provide radiantheat to one of said division walls having radiant steam superheatingsurfaces, and means for regulating each of said burners to adjust theproportion of radiant heat absorbed by said water heating surface and bysaid steam superheating surface to thereby control the temperature ofthe steam delivered by said generating apparatus.

3. A steam generating unit having a combustion chamber dividing wallincluding both water heating tubes and steam superheating tubes exposedat both sides to radiant heat, said tubes being interchangeable in suchmanner that substituting tubes of one type for tubes of the other typein said wall to change the ratio of the water tubes to the superheatingtubes will eflect regulation of the temperature of the generated steam.

4. A furnace for burning powdered fuel to generate steam, comprising ahousing constituting a combustion chamber, a plurality of fuel burnersprojecting into said combustion chamber, and a dividing wall composed ofalternately arranged water tubes and superheater tubes disposed betweentwo of said fuel burners within said combustion chamber.

5. In a steam generating unit, the combination with a combustionchamber, of heat absorbing walls disposed to divide said combustionchamber into compartments, said walls being formed by superheating tubesand water heatin tubes, said superheating tubes being supported by saidwater heating tubes.

6. A steam generating unit comprising a boiler, a combustion chamberdisposed to heat said boiler, water heating tubes connected to saidboiler, and steam superheating tubes connected to receive steam fromsaid boiler, said tubes being positioned vertically within saidcombustion chamber in manner to constitute a division wall therein withboth sides thereof exposed to heat radiated from fuel burning in saidchamber.,

7. A steam generating unit comprising a boiler, a combustion chamberdisposed to burn fuel for supplying heat'to said boiler, steamsuperheating tubes positioned vertically within said combustion chamberin manner to present both sides thereof to heat radiated from fuelburning in said chamber, said tubes being connected to receive steamfrom said boiler for superheating, and

tion with a combustion chamber for the burning of fuel and a pluralityof steam superheating tubes positioned verticallywithin said combustionchamber in manner tocpresent both sides thereof to heat radia d fromfuel burning in said chamber, of a pl ality ofwater heating tubessuspended parallel with and adjacent-to said super- I heating tubes, andmeans carried by said water intermingle and turn upward in the rearportion of said chamber, convection heat absorbing'elements disposedabove the rear portion of said chamber in position to be heated by hotgases flowing therefrom, and radiant heat absorbing elements positionedvertically within the forward portion only of said chamber between saidspaced regions of maximum heat liberation to form walls definingrearwardly openin compartments, said radiant heat absorbing elementsserving to absorb suflicient heat from said regions of maxi-, 'mum heatliberation to reduce the temperature posed top covering a part thereof,a boiler structure disposed over the remainder of said furnace, aplurality of pulverized coal burners in said furnace top adapted toproject burning fuel downward into said furnace, and rows of verticallydisposed heat absorbing tubes arranged in that portion of the furnacebeneath said top and positioned to constitute dividing walls betweenadjacent burners defining open-sided compartments communicatingrearwardly with the undivided part of said furnace, the arrangementbeing such that flames from said burners pass downward between saiddividing walls-'of tubes and then outward through the rearwardlyopening-sides of said compartments into the undivided part of saidfurnace the products of combustion then flowing upward into said boiler.

11. A steam generating unit, comprising an enclosure constituting acombustion chamber, a boiler including water tubes disposed to be heatedby hot gases flowing from said. combustion chamber, a plurality ofburners disposed to project fuel into said combustion chamber at spacedpositions, heat absorbing tubes disposed within said combustion chamberin manner'to constitute dividing walls between the regions of greatestheat liberation resulting from the combustion of fuel projected fromsaid burners, said tubes functioning to absorb suflicient heat tomaintain the temperature within said combustion chamber below that atwhich the ashesresulting from combustion of said fuel would fusesufliciently to adhere to said boiler water tubes, an ash coolingbottomfor said combustion chamber including a member presenting a flatsubstantially horizontal surface disposed to extend between two of saiddividing walls with its edges in spaced relation therewith and servingto receive ashes falling from said combustion chamber," means fortransversely of said furnace and extending from v ashes accumulatingthereon, and means for removing accumulated ashes from said ashreceiving surface into the spaces at the edges of said member adjacentsaid dividing walls at intervals to prevent the accumulation of asuflicient thickness of ashes to interfere with the cooling actio ofsaid cooling member.

12. A boiler furnace having its front and rear walls protected by heatabsorbing tubes, steam superheating tubes disposed on and protecting theend walls of said furnace, a plurality of division walls formed byinterspersed water tubes and superheating tubes said walls beingdisposed the front wall thereof rearwardly parallel with and adjacent tosaid end walls, other division walls formed-by water tubes disposedbetween and parallel with said superheating walls, a; plurality ofburners adapted to project burning fuel into said furnace between saidvarious parallel walls, a boiler disposed to be heated by the productsof combustion from said furnace and arranged to supply steam to saidsuperheater tubes, and means to adjust said burners individually,whereby the degree of superheat of the steam may be regulated bychanging the proportion of the fuel burned adjacent to said superheatertubes to that burned adjacent to'said water tubes.

13. A boiler furnace having its, end walls protected by steamsuperheating tubes, a plurality of division walls formed partly bysuperheating tubes extending rearwardly from the front of said furnaceand parallel with said end walls, and a plurality of burners disposed toproject burning fuel into said furnace between said parallel walls.

14. In a furnace for generating steam, an enclosure constituting acombustion chamber, heat absorbing walls disposed within said chamber'inmanner 'to divide it into compartments, and steam superheating tubescarried by and constituting part of said heat absorbing dividing walls.

15. In a furnace for generating steam, an anclosure' constituting acombustion chamber, a plurality of fuel burners projecting into saidcombustion chamber, and heat absorbing walls disposed between saidburnersto divide said combustion chamber into compartments, said wallscomprising both water heating tubes and steam superheating tubesarranged to be interchangeable, whereby adjustment of the quality of thesteam generated may be efiected by substituting 7 tubes of one type forthose of the other type.

16. A boiler furnace for generating steam, coming elements havingdifferent effects respectively upon the steam being generated, means forintroducing and burning fuel in said sections in such manner that flamesemanating from the open sides of said sections intermingle and equalizein the undivided part of said combustion chamber, means for introducinauxiliary air into each of said sections, means for regulating theadmission of .said auxiliary air into each section to change theposition of the flames therein relative to said radiant heat absorbingelements, and means for absorbing convection heat from hot gases flowingfrom said combustion chamber after the completion of the combustionprocess,

. whereby the quality of the steam being generated may be regulated andthe temperature of the gases flowing from said combustion chamber may bereduced below that at which ashes carried thereby would fuse and adheretosaid convection heat absorbing means, said temperature reduction'being effected by the rapid absorption of radiant heat in said sectionsand said quality regulation being effected by changing the positions ofthe flames relative to said radiant heat absorbing elements, bothwithout detriment to thecombustion process which is completed in theundivided part of said combustion chamber.

17. A boiler furnace comprising a'plurality of open-sided combustionchamber sections lined with radiant heat absorbing elements, means foradmitting burning fuel and air to each of said sections, a maincombustion chamber communieating with said sections for receivingburning fuel emanating therefrom, said chamber being arranged-tofacilitate completion of the combustion process, means for regulatingthe admission of air into each of said sections to controlthe positionsat which the flames pass from the open sides thereof into said maincombustion chamber, and a boiler disposed to be heated by the productsof combustion flowing from said main combustion chamber.

' 18. The method of operating a furnace for gen-,

erating steam in large quantities by the combustion of powdered fuel,that comprises introducing said fuel into a single relatively largecombustion space at a plurality of spaced positions for burninginsuspension, absorbing radiant heat from said burning'fuel at positionsbetween the regions of greatest heat liberation adjacent to said fuelintroducing positions by heat absorbing elements having predeterminedeifects upon the steam being generated, regulating the introduction ofauxiliary air to change the positions at which said fuel burns relativeto said heat absorbing elements for regulating the quality of the steambeing generated, intermingllng the flames emanating from said fuelintroducing positions after they pass beyond said radiant heat absorbingpositions to equalize them for completing the combustion of said fuel,and then abpleted.

19. A boiler furnace for generating steam, comprising a combustionchamber partly subdivided into open-sided sections by radiant heatabsorbing elements having predetermined eflects upon the steam beinggenerated, other heat absorbing elements associated with the undividedpart of said combustion chamber and having other effects upon the steambeing generated, means for introducing fuel into said sections forbuming therein in manner to cause flames to emanate from the open sidesthereof and intermingle in the undivided part of said combustionchamber, means for introducing auxiliary air into said sections, andmeans for regulating the flow of said auxiliary air into each section toadjust the position at which the flames therein emanate from the openside thereof forcontrolling the efiect of said flames upon saidsubdividing heat absorbing elements, whereby the quality of the steambein generated may be regulated.

20. A boiler furnace for generating steam, comprising a combustionchamber partly subdivided by radiant heat absorbing-elements into open--sided sections each communicating with an undivided part'of saidchamber, means for intro- 1 ducing fuel into the tops of said sectionsfor burnsaid sections, and means for adjusting the flow of auxiliary airinto each section in manner to control the position of the flamestherein relative to said radiant heat absorbing elements, whereby thequality of the steam being generated may be regulated.

21. In a steam generating unit, a boiler, a combustion chamberassociated with said boiler, a plurality of heat absorbing divisionwalls disposed vertically within said combustion chamber in position todivide part of said chamber into compartments, said compartments openingat their sides into an undivided part of said chamber, other heatabsorbing elements associated with said combustion chamber, said heatabsorbing elements having different effects respectively upon the steambeing generated, a fuel burner disposed to project fuel into the top ofeach of said compartments for burning therein the flames from saidburners extending from the open sides of said compartments into saidundivided part of saidchamber, auxiliary air inlets disposed to projectauxiliary air into said compartments in direction transverse to saidburner flames, and means to control the flow of said auxiliary air intoeach compartment to regulate the position of said flames therein foraltering the heating effect thereof upon said various heat absorbingelements.

22. In a steam generatingv unit, a combustion chamber, a plurality ofvertically disposed heat absorbing walls arranged to divide said chamberinto compartments, a flat plate extending horizontally across the bottomof each of said compartments between and spaced from said dividing wallsfor collecting ashes falling within said compartment, means to cool saidplates, and means to remove ashes from each of said plates into thespace between each edge thereof and the adjacent dividing wall.

23. In a steam generating unit, a combustion chamber, a plurality ofparallelly disposed dividing walls in said chamber formed by verticallydisposed heat absorbing tubes, means to introduce and burn powdered fuelbetween said dividing walls, a flat member presenting a horizontalsurface disposed to receive ash particles falling between each pair ofsaid dividing walls, said flat members being disposed with 'the edgesthereof spaced from the tubes of the adjacent walls, means for coolingsaid flat members to cool the ash particles falling thereon, and meansfor moving the accumulating ashes from said flat members toward saidwalls to discharge them through the spaces adjacent to said tubes.

24, A dividing wall for a steam generating furnace, comprising aplurality of vertically disposed water'circulating tubes arranged inspaced relationship, a steam superheating tube disposed at each side ofeach of said water circulating tubes, and means securing saidsuperheating tubes'to said water tubes, whereby each of said water tubesserves to support two of said superheating tubes against warping.

25. In asteam generating unit, the combination with a combustionchamber, of a heat abtion with a combustion chamber for burning fuel,

ing tubes to said superheating tube loops in manner to support saidsuperheating tubes to prevent distortion thereof by the heat of thefurnace.

27. A steam generating unit comprising a boiler, a combustion chamberassociated with said boiler, spaced pairs of steam superheating tubesdisposed vertically within said combustion chamber in position topresent both sides thereof to heat radiated from fuel burning in saidchambar, and water heatingtubes disposed vertically within saidcombustion chamber between said spaced pairs of superheating tubes, eachwater heating tube being operatively connected at each side to asuperheating tube for supporting said tubes in manner to preventdistortion thereof by the heat in said combustion chamber.

28. In a steam generating unit having a combustion chamber for burningfuel, a dividing wall disposed to divide said chamber into compartments,said wall being formed by vertically disposed water circulating tubesand steam superheating tubes arranged alternately, said water heatingtubes being supported only at their ends and serving to support saidsteam superheating tubes at intervals throughout their lengths. v

MONTROSE Kl DREWRY.

